Fluid pressure braking system



July 14, 1953 l y N. A. sTEGMAN 2,645,307

FLUID PRESSURE BRAKING SYSTEM Filed June 21, 1949 A'ITORNEY Patented July 14, 1,953

Bendix-Westinghouse Automotive Air Brake Company, Elyria, Ohio, a. corporation of Dela- Ware Application June 21, 1949, Serial No. 108,425

rlhis invention relates to iiuid pressure braking systems lor tractor-trailer vehicles andmore particularly to braking systems embodying safety features for conserving fluid pressure on the tracl the copending application of Ellery R. Fitch et al. y

led June 21, 1949, Serial No. 100,498for Tractor Protection Valve for Braking Systems and owned by the same assignee as the present application, a-novel system is disclosed for shutting off communication between the tractor and trailer emergency and service lines in the event of a break-in-two of the vehicles; In the copending application, the interruption of the fluid ilow between the vehicles is controlled by the pressure in the tractor reservoir when such pressure'reaches a predetermined low value. Under such conditions, further loss of pressure from the tractor braking system is prevented, and the tractor may be quickly andV eiciently braked underv the control of the operator.

lWhen theiiiow of fluidbetween the vehicles is interrupted in theicopending application, as stated above, the construction is such that the trailer emergency line is vented to atmosphere which causes an emergency application'of the trailer brakes in well known manner. This action is desirable where the interruption follows a break-in-two or the development of a severe leak in the emergency line. However, in certain instances,` as for example,` when the tractor reservoir pressure falls below the pressure necesgency brake application arising'from a decrease. in the pressure of the fluid in the tractor res- .tem in order to 2 A` further object is to provide a novel and efficient control of the separate source whereby the operator lmay readily effect release of the undesired emergency trailer brake application.

Other objects and novel features of the invention will appear more fully hereinafter from the followingvdetailed description when taken in connection with the accompanying drawing illustrative of one form of the invention. It is to be expressly understood however that the drawing is utilized for purposes of illustration only and is not to be taken as a definition of the limits of the invention, reference being had for Vthis purpose to the appended claims.

Referring to the drawing, the single ligure diagrammatically illustrates the present invention in connection with a tractor-trailer braking system, certain of the parts being shown in section.

As shown, the present invention is utilized in connection with a tractor-trailer braking system of the type disclosed in the aforementioned copending application. More particularly, the tractor braking system includes a compressor I0 for supplying compressed air through conduits I2 and I4 to alpair of serially connected reservoirs I6 and I8, the loading and unloading of the compressor being preferably controlled by a governor 20 which may be constructed as shown in the patent to B. S. Aikman, No. 1,754,218 dated April 15, `1930. Front and rear brake chambers 2|- and"23 areprovided for applying the tractor brakes and these chambers may be supplied with air pressure? from the reservoir I8 through conduits 22, 24, 26, 28, 30, 32, 34, 36 and 38, a suitable pedal-operated brake valve 40, which may be constructed as shown in the patent to W. J. Andres et al. No. 2,133,275 dated October 18, 1938, being associated with the conduits 24 26 and 34, for controlling the degree of brake application. A

In order to provide suitable connections for the trailer braking system, the tractor braking system includes an emergencyline 42 comprising conduits 44, 4B, 48 and 50, as Well as a service line 52 which includes conduits 54 and 56.

The emergency and service lines 42 and 52 ter.-

minate in coupling parts of well known construction which are adapted to be coupled with similar parts associated with the trailer braking sysprovide releasable couplings 58 and 60.

The trailer braking system includes a plurality of `brake chambers 62, an emergency line 64, a service line 66 and a trailer reservoir 6B, all of theforegoing being interconnected through a S6 is connected and 'an emergency valve portion to which the emergency Aline 64 is connected. The operation of the valve 10 is such that it normally connects the emergency line 64 with the reservoir 68 tomaintain the latter charged With air pressure from the tractor reservoir I8 and also connects the trailer reservoir' 68- with the brake chambers 62 through conduits 12 and 14 whenever the service line 66 is chargedfthroughy operation of the tractor brakevalve; 40. in the event of a break in the emergency line 64, as for example, during a break-in-two of the vehicles, the Valve 10 would function to supply air pressure to the brake chambers 62 from the reservoir 68 to eiect an emergency application of the trailer brakes. p

` From the foregoing, it will be.appreciated that inV operation, should the vehiclesy Vbecome separated, or should a severe leak occur inthe emergency or service-lines of. either vehicle, the air pressure supply in the tractor reservoir may be. depleted so rapidly as to prevent ecient application o'f the tractor brakes. Means are provided for overcoming this'diiculty in a manner which will appear more fully hereinafter.

, More particularly, such means includes an arrangement for interrupting the communication between the tractor and trailer emergency and service lines in the event that the tractor reservoir pressure drops to a predetermined value. Asshown, the arrangement comprises a tractor protection valve device 16 that includes check valves 18 andai) which are respectively positioned in the tractor emergency and service lines 42 and 52 and which are arranged tovberclosed byA springs 82 and 84 in the direction of air flow. As shown, the valve devicerl comprisesa body 86 .provided with emergencyrinlet and outlet connections 88jv and 90 which are respectively connected with the conduits 46Vand 44, Vthe emergencyv chekvalve18 being positioned in an inlet chambertY and normally urged bythe; spring 82 w e.;.psition. where communication between the inlet'connectionand the outlet vconnection 9|)4 is interrupted.; At its lower-end, they body, 8|3' is provided with an inletchamber M WhichA communicates Ywith the conduit by Wayof an inletconnection 9,5. The service checkvalve, andthe spring 84 are positioned` within the,

chamber. 94, and as has heretofore been pointed out,theaction of .the spring84 is `suchasto tend to close thevalve 80V in the directionof '.airiiow. in order to interrupt communication between conduits,56 and 54. When valve 80is. opened,

by stein 98, conduits 56 and 54 are connectedby..

way of .connectionA 95 and chamber 94, the latter communicating with an outlet connection |00 by, wayzopfibore vI 0.2;.and ,ducts I 0.4 4formed in a spool member. |06.

Means are provided foncontrolling the opera. tion of the check valves .18 :and 80 inaccordance W-ithvariations in the.. tractor reservoir prese sure. As. shown, such means includes. a. diaphragm. 08 which .is .clamped between the -body- 86 and a cap |.I0 .andwhich formsa. diaphragm chamber and an exhaust chamber ||3 at .the upper portionofwtheyalve device;16. A... valve actuating., element I. II2 is secured. to the; diag..

Also.

ohragm I 08and .siormed with abore .I I 4. which commpnicates wat... all times with the... exhaust..

4 chamber ||3 through a plurality of openings H6. With the parts in the position shown, a diaphragm spring ||8 is effective to move the diaphragm |08 and element II2 upwardly to connect the emergency line 42 to an atmospheric port |20 by way of the outlet 90, bore I|4, openings ||6 and the exhaust chamber II3. Under these conditions, r the emergency check valve 18 and the service check valve 'are closed. However, when the diaphragm |08 is moved downgovernorA |24, conduit |26 and conduit 22. TheY governor |24is preferably like the governor 20 and isset to cut-out and cut-in at any prede-` termined desirable range. In practice, it has beenV determined that excellent results are 0btained with a 50 p. s. i. cut-in pressure and a 75 p. s. i. cut-out pressure.

cut-out and cut-in pressures Vis sufficient to permit the tractor and trailerreservoirs I8 and 68 to equalize and still keep the equalizing. pressure.

above the 50p. s; i. cut-in pressure.

In operation, and assuming that theV parts occupy'the positions illustratedwith no air in the system, it will be seen that the emergency and service valves 418V and 80 areV closedA and that the emergency line 42 Ais connected withV the atmospheric port |20. Under these` conditions, the trailer brakes 62 are automatically connected with the trailer-reservoirthrough the relay-emergency valve 10.v As the air pressure is builtup in thetractor reservoirIB, through operation of the compressor I0, lthe valve device 1 6 Will remain in its illustrated position until the pressure inthe reservoir I8 has reached the 75 p.- s; i. cut-lout Y pressure. At this pressure the governor |24 cuts out and connects conduitsv|23ar1d I26,Vthus ,deliveringair to vthe diaphragm chamber at '75v p., s.; i., andcausing; the diaphragm |08' to move downwardly.V This action closes; the 'exhaust Valve |22 and openstheernergency and service.

valves. 18 and 80 against the action ofA their respective springs 32Y and 84, Athusinterconnecting. the. vehicle emergencvflines` 42 and 64 to allowthe trailer reservoir pressuregtdbuild up,.aswel1 as interconnecting the vehicle Vservice lines- 52,

and 66.

When the systemis inzop eration, with all ,res-.1 ervoirsiullyA charged, .itwilll be readily under-- stood that .so longasthe lpressurein the-.-tractor reservoir l'zisabove .the 50 p.V s., i. cut-in pres-, sure of the governor |24, theoperation of the, tractor and trailer brakesin service isunderthe;

completecontrol of the .operatorthrough the brake valve 20. In;the vevent however, of leak-J age. :from .the tractor reservoir, due vto .any bro-.-

ken line.. on either vehicle, ofsuch extent as toi. cause. .the tractor reservoir pressure to drop'ito. the.50 p. s. i. cut-.inv pressure, .it.will.be .under-1. stood thatin suchzevent. the governor. |241wi11. operate to cut off the conduit |26 and to connect?.v`

It will be understoodV h owevelxpthat this rangepis byway of example,- only, and'that other pressuresmay-be employedk if desired. The 25 p. s.`i. diierential between thethe conduit |23 with an atmospheric port at .the governor. This action exhausts the diaphragm chamber permitting the diaphragm |08 and element ||2 to move upwardly to connect the emergency line 42 with the atmospheric port |20,

Should the trailer emergency line break or develop a severe leak, the pressure in such line will exhaust and cause an emergency application of the trailer brakes by reason of the automatic operation of the relay-emergency valve 10. thev emergency valve 18 is open, the pressure in the tractor reservoir |8 will bleed down through the break until the 50 p. s. i. cut-in pressure of the governor |24 has been reached. At this point, the governor |24 functions to exhaust the diaphragm chamber of the valve device 16 and the emergency and service valves 18 and 80 will close in order to conserve the tractor reservoir pressure.

In the event that the trailer service line B6 should break or develop a severe leak, a brake application by the operator which would reduce the tractor reservoir pressure through the broken line to the 50 p. s. i. cut-in pressure of the gov-` ernor |24 would cause operation of the valve device 16 in the manner heretofore described to close the emergency and service valves 18 and 80. Here again, the tractor reservoir pressure would be conserved between 50 and rI5 p. s. i.

All of the foregoing is disclosed and claimed in the copending application referred to above.

The present invention includes an arrangement which is particularly adapted for use in the system heretofore described and which is ef- `fectve to release the trailer brakes in the event of an undesired emergency application due to the pressure in the tractor reservoir IB being less than the low pressure setting of the governor |24. As shown, such arrangement includes an over-ride reservoir |30 which is connected with the tractor reservoir I8 by means including a One-way valve |32 permitting ow of air from the reservoir I8 to the reservoir |30 only.v Hence, full reservoir pressure from the reservoir I8, which may be of the order of 105 p. s. i., is conducted to the reservoir |30 and maintained therein. A two-way valve |34, which is mounted in such position as to be readily accessible to the operator, is connected with the over-ride reservoir |30 by conduit |35, and is also connected with the governor |24 and with the emengency inlet connection 88 by conduits |36 and |38 respectively. These latter connections include double check valves |40 and-|42 of well known construction which allow flow of air from either of two sources to a` single outlet.

Normally, the two-way valve |34 occupies a position where the conduit |35 is closed 01T and the conduits |36 and |38 are open to atmosphere. In the event however, of an undesired emergency application of the trailer brakes due to the pressure in the tractor reservoir I8 being below the low pressure setting of the governor |24, the valve |34 may be operated to connect the con- Since Y 6 duits |36 and |38 withA the over-ride reservoir |30. Under these conditions, full reservoir pres, sure, which may be of the order of p. s. i.. is conducted to the governor |24 and. to the emergency inlet 88. The governor |24 will promptly trip and apply full pressure to the diaphragm chamber to cause the tractor protection valve to operate to open the emergency and service valves 18 and 80. As soon as the emergency valve 18 is opened, full pressure fromA the over-ride reservoir |30 will be delivered to the interconnected emergency lines 42 and 64 to release the emergency application of the trailer brakes due to the previous operation of the re.`

lay-emergency valve 10. Y

From the foregoing, it will be readily seen tha the present invention `provides a relatively simple but highly effective construction for releasing an undesired emergency brake applicationl on the trailer due to a pressure in the tractor reser-` voir which is lower than the low pressure setting of the governor which controls the tractor protection valve. The use of the over-ride reservoir |30 and its one-way connection assures a separate source of uid pressure on the tractor for operation at any time in the manner described.

While one embodiment of the invention has been shown and described herein, it will be readily understood by those skilled in the art that various modifications may be resorted to without departing from the spirit of the invention. Reference willy therefore be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

l. In a tractor-trailer braking system having a iiuid pressure operated braking system on the tractor, a fluid pressure operated braking system on the trailer, and means comprising ernergency and service lines respectively connecting the tractor and trailer systems, said tractor braking system including a reservoir of fluid pressure, valve means for controlling communication between said emergency and service lines, means sponsive means to said second reservoir to sepa` rately control said valve means.

2. In a tractor-trailer braking system having a fluid pressure operated braking system on the tractor, a fluid pressure operated braking system on the trailer, and means comprising emergency and service lines respectively connecting the tractor and trailer systems, said tractor braking system including a reservoir of fluid pressure. valve means for controlling communication between said emergency and service lines, means V tractor, a fluid pressure operated braking sys-` tem on the trailer, and means comprising emergency and service lines respectively connecting the tractor and trailer systems, said tractor braking system including-'a reservoir of uid pressure,- valve means for controlling communication between said emergency and service lines, means responsive to a ii'rst predetermined pressure at said reservoir for opening said valve means and responsive to a second predetermined pressure at said reservoir, less than said first pressure, for closing said valve means and for connecting the trailer emergency line to atmosphere, a second reservoir of fluid pressure, means for maintaining at all times the pressure in said second reservoir at a value higher than said rst predetermined pressure, and manually controlled means for connecting said responsive means to said second reservoir to separately open said valve means, disconnect the trailer emergency line from atmosphere, and connect said latter'line to the lsecond reservoir.

4. In a `tractor-trailer braking system having a fluid pressure operated braking system on the tractor, a iiuid pressure operated braking system on the trailer, and means comprising emergency and service lines connecting the tractor and trailer systems, means including a tractor fluid pressure reservoir for supplying fluid pressure to the tractor and trailer braking systems, means responsive to a reduction in the pressure of the iiuid in the tractor reservoir to a predetermined low value for causing an emergency application of vthe trailer braking system, a second tractor iiuid pressure reservoir, means for maintaining at all times the pressure in said second reservoir at a value higher than said predetermined low value, and means including said second reservoir for releasing said emergency application.

5. In a tractor-trailer braking system having a fluid pressure operated braking system on the tractor, a uid pressure operated braking' system on the trailer, and means comprising emergency and service lines connecting the tractor and trailer systems, means including a tractor fluid pressure reservoir for supplying fluid pressure to the tractor and trailer braking systems, means including a device on the tractor responsive to a reduction in the pressure of the fluid in the tractor reservoir to a predetermined low v value for venting the trailer emergency line to atmosphere and causing an emergency application ofY the trailer braking system, va second tractor fluid pressure reservoir, means for maintaining at all times the pressure in said second reservoir at a value higher than said predetermined loW value, and means for connecting said device and second reservoir to disconnect the trailer emergency line from atmosphere, and connect the latter line and second reservoir to release the emergency application.

6. YIn a tractor-trailer braking system having 8 a fluid pressure operated braking system on the tractor, a fluid pressure operated braking system o-n the trailer, and means comprising emergency and service lines connecting the tractor and trailer-systems, a tractor iiuid pressure reservoir, conduit means connecting said reservoir and the trailer Yemergency line, an emergency valve in said conduit means, other conduit means connecting said reservoir and the trailer service line, a service valve in said other conduit means, means including a uid pressure responsive device operable when the reservoir pressure reaches a predetermined low value for closing both said valves and for connecting the trailer emergency line to atmosphere, and oper-able when the reservoir pressure reaches a predetermined high valuefor closing the connection Ibetween the trailer emergency line and atmosphere and for opening both said valves, a fluid pressure governor for connecting said reservoir to said device when vthe reservoir pressure reaches said predetermined high value and for disconnecting said reservoir and device when the reservoir pressure reaches said predetermined low value, means connected with said trailer braking system for causing an emergency trailer brake application .when said device connects the trailer emergency line to atmosphere, and means for releasing said emergency trailer brake operation at will comprising a second tractor reservoir of fluid under pressure, means for maintaining the pressure of the fluid in the second reservoir at a value higher than said predetermined high value, and manually operable means for simultaneously connecting said pressure responsive device and said rst named conduit means with Vsaid second reservoir whereby said device operates to close the connection between the tra-iler emergency line and atmosphere and to open both said valves and whereby iiuid from said second reservoir is conducted to the trailer emergency line past the open emergency valve.

7. A tractor-trailer braking system of the References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,614,652 Christensen Jan. 18, 1927 2,684,707 Robinson June 22, 1937 2,232,883 Neveu Feb. 25, 1941 2,451,139 Williams et al Oct. 12, 1948 

